title: Effects of lung volume and involuntary breathing movements on the human diving response.
abstract: The effects of lung volume and involuntary breathing movements on the human diving response were studied in 17 breath-hold divers. Each subject performed maximal effort apnoeas and simulated dives by apnoea and cold water face immersion, at lung volumes of 60%, 85%, and 100% of prone vital capacity (VC). Time of apnoea, blood pressure, heart rate, skin capillary blood flow, and fractions of end-expiratory CO2 and O2 were measured. The length of the simulated dives was the shortest at 60% of VC, probably because at this level the build up of alveolar CO2 was fastest. Apnoeas with face immersion at 100% of VC gave a marked drop in arterial pressure during the initial 20 s, probably due to high intrathoracic pressure mechanically reducing venous return. The diving response was most pronounced at 60% of VC. We concluded that at the two larger lung volumes both mechanical factors and input from pulmonary stretch receptors influenced the bradycardia and vasoconstriction, resulting in a nonlinear relationship between the breath-hold lung volume and magnitude of the diving response in the near-VC range. Furthermore, the involuntary breathing movements that appeared during the struggle phase of the apnoeas were too small to affect the diving response.
authors.affiliation: Department of Animal Physiology, Lund University, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Andersson
authors.forename: E
authors.initials: E
authors.lastname: Schagatay
mesh_terms: D000328:Adult; D001049:Apnea; D001783:Blood Flow Velocity; D001794:Blood Pressure; D002196:Capillaries / Q000502:physiology; D003080:Cold Temperature; D004242:Diving / Q000502:physiology*; D005145:Face; D006339:Heart Rate; D006801:Humans; D007101:Immersion; D008168:Lung / Q000502:physiology*; D008176:Lung Volume Measurements; D008297:Male; D009068:Movement; D012119:Respiration / Q000502:physiology*; D012867:Skin / Q000098:blood supply